Signal processing circuit, signal processing method, optical receiver and optical communication system

A signal processing circuit, comprising:

• optical frequency deviation estimating means
• for inputting a plurality of signal data that are generated by mixing a plurality of optical carrier waves with a local light which optical carrier waves are phase-modulated and have polarizations able to be demultiplexed from each other, and that signal data corresponds to the polarizations of the optical carrier waves respectively, and
• for estimating a frequency deviation included in each the input signal data and is a difference between a frequency of the optical carrier wave and a frequency of the local light, per the signal data;
• optical frequency deviation compensating means for making a phase of the signal data rotated correspondingly to the frequency deviation;
• optical phase deviation estimating means
• for estimating a phase deviation included in each the input signal data and which is a difference between a phase of the optical carrier wave and a phase of the local light, per the signal data, and
• for outputting the estimated phase deviation as an estimated value;
• optical phase deviation amount compensation analyzing means for calculating an amount of phase compensation which is an amount of compensation to make the phase of the signal data rotated so as to reduce the phase deviation, on the basis of a plurality of the estimated values estimated per the signal data;
• and
• optical phase deviation compensating means for making the phase of the signal data rotated correspondingly to the amount of phase compensation.

A signal processing circuit:

• comprising:
• an optical phase deviation compensation amount analyzing means
• for inputting a plurality of signal data that are generated by mixing a plurality of optical carrier waves with a local light, which optical carrier waves are phase-modulated and have polarizations able to be demultiplexed from each other, and that corresponds to the polarizations of each of the optical carrier waves, and
• for calculating an amount of phase compensation which is used for making a phase of the signal data except for a first signal data out of the input plural signal data rotated so as to reduce a frequency deviation between a frequency of the optical carrier wave and a frequency of the local light, on the basis of the first signal data.